The present invention relates to an alloyed steel and, more particularly, to an alloyed steel having high resistance to heat and wear and high strength at high temperature.
The present invention pertains to the alloyed steel which is suited as a material for rails or like guides of a type installed on the hearth within a heating furnace.
An alloyed steel, identified by UM Co-50 alloy, which contains 0.12% carbon, 1.10% silicon, 1.05% manganese, 0.013% phosphorus, 0.08% sulfur, 31.0% chromium, 50.8% cobalt and iron as the remainder, is known to have high resistances to heat, wear and sulfuration. Because of these properties, the UM Co-50 alloy has heretofore been largely employed as a material for rails or as guides of a type installed on the hearth within a heating furnace for heat-treatment of slabs of metal. However, it has recently been found that the UM Co-50 alloy involves some disadvantages which will now be described.
One disadvantage is that, although the UM Co-50 alloy which has been used in the furnace for reheating the slab of metal wherein the temperature is within the range of 1,100.degree. to 1,250.degree. C. exhibits a satisfactory performance, it is susceptible to cracking when exposed at the temperature of not more than 1,100.degree. C. during preheating, because of change in structure such as formation of the .sigma.-phase.
Another disadvantage is that the UM Co-50 alloy exhibits poor welding properties. One reason for this thought to be the presence of an eutectic within the grain boundary and the dendrite tends to invite cracking in a heat affected zone formed during welding. Another reason for this is thought to be that the deformability and form of the .epsilon.-phase band cause cracking in the crystalline structure.